The invention relates to a seam formed between when two or more laminates are joined together.
High technology apparel garments made of waterproof textile laminates are state of the art. These laminates contain a waterproof, windproof and breathable membrane onto which is laminated at least one textile layer.
The joining together of two textile laminates present a problem if the seam at which the two textile laminates are to be sealed is to be made waterproof. Various methods have been tried. For example, W.L.Gore and Associates has developed a method in which two GORE-TEX(copyright) laminates are heat sealed at a seam using a GORE-SEAM(copyright) seam sealing tape.
The principles of sealing are well known. Generally, to get a sealed joint or a seam, a sealant, an energy source, and structural joining are required. There are a number of prior art methods which demonstrate this. The sealants available are numerous and can be added to the laminates or are part of the native materials. The energy sources which can be used for sealing are numerous and include, but are not limited to heated tools, radio frequency, thermal impluse, and ultrasonic welding methods. Under the proper conditions structural joining of the textile laminates will take place and a joint or seam will be formed.
The prior art discloses a number of seam-forming methods involving the fusion of a thin strip of thermoplastic material to bind two layers of textile materials together and thus form a seam. These are disclosed, for example, in U.S. Pat. No. 3,387,307 (Blatz) assigned to Handgards, Inc. A similar method is taught in GB-A-1 465 343 in which a thin thermoplastic strip is placed between two fabric pieces to form the seam. The use of this method results in a stiff seam being formed between the two fabric pieces.
Other prior art is known in which the laminates are adhered together using adhesives. European Patent EP-B-0 345 730 (Kleis) assigned to W.L.Gore and Associates GmbH teaches the use of adhesive beads to produce the seams in a glove or other clothing application. Glove insert products made according to this invention are available from W.L.Gore and Associates GmbH in Feldkirchen, Germany, under the trade mark DIRECT GRIP(copyright). In order to ensure absolute waterproofness of the seams, it is necessary for the adhesive to penetrate the whole depth of the textile layer up to the membrane. In particular for voluminous textile layer, the seams have to be glued over a wide area. The seams thus produced are strong but relatively stiff and uncomfortable.
U.S. Pat. No. 5,003,902 describes a seam construction for use on protective clothing which involves overlapping the fabric pieces and bonding them together by use of a melt-adhesive film between them. A liquid-proof thread is sewn through the overlap in order to secure the two pieces of fabric to each other. The completed seam is then heated to melt-bond the adhesive film to the fabric pieces and to seal any apertures left by the sewing thread. The seams produced according to the teachings of this patent are also strong but relatively stiff and therefore uncomfortable to the wearer.
One of the problems encountered with these prior art seam sealing methods for waterproof laminates is that the seams have had to be fairly wide in order to ensure that the seams are waterproof. This results in a stiff seam which reduces the comfort of the garment to the wearer. In, for example, sock or glove applications, the width and/or the stiffness of the seams is particularly noticeable. Some attempts have been made at producing narrower seams. However, these have not been durably waterproof or softer because of the added sealant material.
It has been possible with prior art methods to construct narrower seams which are waterproof and flexible. However, these seams have proven to be weak in the transverse, i.e. cross-seam, direction. This weakness results in a lack of durable waterproofness.
U.S. Pat. No. 3,625,790 (Ayres) teaches a glove made of a non-breathable laminate of an elastic fabric and a thermoplastic layer. Two pieces of a laminate are welded together to form a glove in which the seams are formed by fusion of the thermoplastic layers using dielectric heating means. The use of electromagnetic waves at radio frequencies to form seams limited to those materials textiles which incorporate materials having dipolar molecules, such as polyvinyl chloride (PVC) or some polyurethanes (PU). This insert seam while flexible is not very strong. Particularly in manufacturing processes this is a severe disadvantage since the textile laminates have to be handled carefully in order to avoid damage.
Further prior art known to the inventors includes U.S. Pat. No. 4,545,841 (Jackrel) which teaches an insert that is formed by heat sealing and U.S. Pat. No. 5,036,551 (Dailey) which teaches a glove that is formed by heat sealing a laminate. In both these examples, the insert seam while flexible is not very strong.
The problem with the prior art examples in which sealant material is added to form the seam is that the seam whilst strong is not flexible, i.e. they feel stiff to the wearer. The use of these seams is thus limited because of the discomfort to the wearer, especially in those applications in which a close fit is required.
The problem with the prior art examples in which the sealant material is supplied from the native material is that the seams whilst flexible are weak. The use of these seams is limited because of durability in tough applications and, particularly in manufacturing processes this is a severe disadvantage since the textile laminates in which such seams are incorporated have to be carefully handled in order to avoid damage.
Further problems with prior art seams, such as those made from polyamide or polyester is that these materials tend to shrink when these materials are heated to their melt points. This causes the laminates to deform.
There is therefore a need for a strong, durable and flexible seam for tough end uses and close fitting applications.
It is therefore an object of this invention to improve the comfort of the seams in garments made of waterproof laminates.
It is furthermore an object of this invention to reduce the width of the seams in garments made of waterproof laminates.
It is therefore an object of this invention to produce long-lasting, durable seams in garments made of waterproof laminates.
It is furthermore an object of the invention to provide seams which are both strong and flexible.
It is furthermore an object of the invention to provide seams which are strong in the transverse (cross-seam) directions.
A further object of the invention is to provide seams which have a low shrinkage.
A further object of the invention is to provide seams which have a high stretch.
It is preferred that the laminates from which the seams are to be made are breathable, i.e. water vapour permeable.
These and other objects of the invention are solved by providing a laminate with a waterproof and preferably breathable functional layer on which is laminated a second textile layer comprising at least a first component and a second component, preferably in the form of a conjugate fibre. The first component is made of a material which is stable to a first temperature and the second component is made of a material which melts at a second temperature. The first temperature is higher than the second temperature. Such a laminate can be supplied with energy, e.g. by heating, to reach a temperature higher than the second temperature but lower than the first temperature. The second component melts and provides sealant material (adhesive) for joining the laminate to another substrate or a laminate.
Both the first component and the second component participate in the structural joint. The second component encapsulates the first component whilst the first component remains stable. The second component provides the waterproof barrier and the first component provides structure and strength to the seam.
Using these laminates, it is not necessary to use an additional thermoplastic strip to provide adhesive material to form the seam. Rather the material of the laminate (the native material) forms the seam itself. This leads to a reduction in manufacturing complexity of the seam and a reduction in seam bulk thus reducing the stiffness of the seam and increased comfort to the wearer. There is also an improvement in the assembly at the factory making, for example, gloves with seams of the invention since these seams are more tolerant of external stresses.
The seams formed by this laminate are found to be high in transverse seam strength and longitudinal strain and also to be flexible.
Such laminates are known from U.S. Pat. No. 5,662,978 (Brown et al.) assigned to Kimberly-Clark Worldwide, Inc., and in which conjugate spunbound fibres of polypropylene and polyethylene are used to form a non-woven textile layer. This textile layer is laminated to a polyolefin film, particularly polyethylene. The laminates formed according to the teachings of this patent are used for manufacturing a protective covers and not for the production of articles of clothing. There are no teachings in this patent that the laminate of this invention can be used to form comfortable and hard-wearing seams, such as those used in the production of articles, e.g. articles of clothing.
A similar laminate is further known from U.S. Pat. No. 5,503,907 (Gessner) assigned to Fiberweb North America, Inc., in which a non-woven textile layer of multi-component fibres is laminated to a microporous layer. The lower melting component of the multi-component fibre taught in this patent application is used to form the bond of the textile layer with the microporous layer. The higher melting component retains its substantially continuous fibrous form to provide a strengthening and reinforcing function in the laminate. There are no teachings in this patent concerning the production of seams from laminates used, for example, in clothing applications.
Similarly German Patent DE-C-196 32 312 (Tebbe) teaches a glove made of a laminate of a polypropylene foil onto which is laminated a textile layer of cotton or cellulose. The textile layer further includes polypropylene fibres in a blend in order to improve the adhesion between the polypropylene foil and the textile layer. The glove is made by welding two pieces of laminate cut on the polypropylene foil side into glove shapes together by radio frequency welding. In this example, the textile layer is placed on the exterior of the glove and the polypropylene foil is on the inside of the glove. The textile layer thus does not participate in the welding together of the two textile laminates.
The seams formed from the laminates of the invention are sufficiently waterproof that they are able to withstand a water entry pressure of at least 0.07 bar and preferably at least 0.13 bar according to the suter test described below. Furthermore the seams are strong and flexible as demonstrated by the stiffness tests and the Instron tests below.
In the laminate, the second (low melting point) component is preferably meltable at a temperature in the range from 80xc2x0 C. to 170xc2x0 C. whilst the first (high melting point) component is stable to a temperature of at least 140xc2x0 C. For a reliable seam to be formed the difference in temperature between the first temperature and the second temperature is at least 20xc2x0 C.
In one embodiment of the invention, the second layer further includes a propellant or foaming agent which is activatable by activation means. On activation this propellant produces a gas which in combination with the melted second component provides a foam-like substance with closed cells. The closed cells ensure that the seam remains waterproof but the seam is resilient but also xe2x80x9cspongyxe2x80x9d and thus soft. The seam is therefore comfortable for the wearer of apparel made from the laminate.
According to one embodiment of the invention the second layer is composed of a plurality of yarns in the form of strands, filaments, threads or fibres. The second component in the second layer is a thermoplastic which is selected from the group of thermoplastics comprising co-polyester, polyamide, co-polyamide or polyolefin. In the preferred embodiment of the invention the second component is a polyethylene a polyamide 6.0.
The first component is selected from the group of polymers comprising cellulose, protein fibers including wool and silk, polyolefins including polypropylene and polyethylene, polyester, co-polyester, polyamide or co-polyamide. Preferably the first component is polyamide 6.6.
The yarn in the second layer is in one embodiment a conjugate fibre comprising the first component and the second component. A conjugate fibre having two components is sometimes termed a bi-component fibre. Suitable bi-component structures for use in the invention include an eccentric-sheath-core configuration, a concentric sheath-core configuration, wherein the second component forms the cover, an xe2x80x9cisland-in-seaxe2x80x9d configuration, a wedge-core configuration, a wedge configuration or a xe2x80x9cside-by-sidexe2x80x9d configuration. In the preferred embodiment of the invention, the fibre used has a sheath-core configuration.
In the embodiment of the invention with a propellant, the propellant is activated at a third temperature, the third temperature being intermediate between the second temperature and the first temperature. The propellant can be an integral part of the second component and is selected from the group of propellants consisting of azodicarbonamide, ammonium hydrogen carbonate, toluolsulfohydrazin or diazoaminobenzol. In the preferred embodiment of the invention the propellant is azodicarbonamide.
The functional layer included in the laminate is a membrane or a film. The functional layer is selected from the group of materials consisting of polyester, polyamide polyketone, polysulfones, polycarbonates, fluoropolymers, polyacrylates, co-polyetheresters, co-polyetheramides, polyurethane, polyvinylchloride (PVC), polytetrafluoroethylene or polyolefins Preferably the functional layer is made from expanded PTFE. Expanded PTFE is known to be very waterproof and highly breathable. It provides the laminate with an water vapour transmission rate of less than 150 (m2.Pa)/m and a water entry pressure of greater than 0.13 bar.
The invention also provides a method for sealing detected pinholes in waterproof laminates by allowing one component in the textile layer to be melted to flow and seal the detected pinhole.